U.S. patent application Ser. No. 507,162 discloses a system for modifying the shape of a three dimensional object such as a tooth in a patient's mouth. The system includes a pantograph type assembly for feeding to a computer digitized data representing surface contours of the tooth. The pantograph assembly includes a hand-held probe inserted into the patient's mouth by a dentist. The dentist manipulates the probe so that a stylus tip of the instrument is held in contact with the tooth during tracing of a contour along the tooth. A pantograph extension outside the patient's mouth tracks the motion of the probe and particularly the stylus tip thereof, the motion of the pantograph extension being monitored by cameras which transmit video signals to the computer.
In an alternate embodiment of the contour data gathering device dislosed in application Ser. No. 507,162, an articulated arm assembly is fastened at a proximal end to a stationary fixture, while a distal end of the articular arm assembly carries a dental probe or drill. A plurality of digital encoders are operatively connected to the arms of the articulated assembly for providing respective electronic feedback signals which are fed to a computer. The computer uses the electronic feedback signals to calculate the position and orientation of the dental probe or drill.
In the articulated arm assembly, it has been observed that inaccuracies may creep into the computations of probe position and orientation. These inaccuracies are attributable in part to incremental flexures in the various arms of the articulated assembly and to changes in size owing to temperature effects.
The accuracy of the position and orientation computations is particularly important when the data is being used to calculate optimal locations and oreitnations of implant anchors or blades. Dental implants constitute a relatively recent development in dental practice and/or treatments. In an implant, the jaw bone of a patient is drilled to form a bore which receives a blade or anchor for an implant crown. To produce a desired and proper osseo integration and prosthetic and/or restorative placement of supra gingival restoration on the implant in its functional occlusal position, the dental practitioner or surgeon must precisely control the position, orientation and insertion of the blade or anchor. The ultimate position and orientation of the blade must take into account the thickness of the bone at the area of the implant, the proximity and orientation of adjacent teeth in the same jaw, and the location of teeth in the opposing jaw. In proper conventional implantation surgery, two or three people view the drill from different angles, to determine that the drilling is at a proper angle and location. Even under these circumstances, it is difficult to control the drilling operation so that the position obtained and orientation of the implant blade is optimal or acceptable.
Prior application Ser. No. 743,103 discloses a method and apparatus for facilitating the optimal placement of dental implant anchors. However, as noted above, the accuracy of the procedure is limited to some extent by the the equipment.